PROJECT SUMMARY Invasive fungal infections are an important cause of morbidity and mortality for people with compromised immunity. Unfortunately, the mortality associated with invasive fungal infections remains unacceptably high. One of the contributing factors to this poor outcome is the fact that there are relatively few therapeutic options for the treatment of invasive fungal infections, particularly when compared to the number of antibiotics available for the treatment of bacterial infections. To identify new antifungal drug candidates, we have initiated a high throughput screening and chemical biology-based project to identify molecules that interfere with fungal cell wall biosynthesis. Application of this strategy has rapidly led to the identification of human phosphoinositide dependent kinase-1 (PDK1) inhibitors as highly active antifungal molecules in vitro. PDK1 inhibitors have been extensively developed as targeted anticancer molecules because of their low toxicity toward normal cells and, encouragingly, three of the PDK1 inhibitors identified in our preliminary work (UCN- 01, sunitinib and OSU-03012) have been, or are being, evaluated in human clinical trials. In order to develop the promising potential of PDK1/Pkh inhibitors as antifungal drugs, we will: characterize the molecular basis for the activity of mammalian PDK1 inhibitors toward fungal PDK1 orthologs (Aim 1); optimize the antifungal activity of two lead scaffolds (pyrazole and oxyindole/istatin) by structure-activity analysis (Aim 2); and determine the in vitro and in vivo efficacy of the novel PDK1 inhibitors in animal models (Aim 3). This focused research plan is designed to systematically evaluate the antifungal activity of human PDK1 inhibitor scaffolds and will hopefully lead to first-in-class antifungal molecules for additional development.